SD and CF Cards together in 5D Mark III

[RedStateRon]

Have 32 GB SD card (45 MB -speed)
Depending on answer, may want to get a CF Card 32 GB (with faster speed)

Read that if both used at same time (not one or the other) then the speed becomes that of the lowest card. True?
I realize there are many different reasons to have two cards as well as speed of cards. I am not a professional, but at least would be considered intermediate. Used to shoot print film years ago (60-70s) eyesight became poor, got cataract surgery now eyes good again, and the AF on the 5D MIII propelled me to re-enter photography. My lens is good too, 24-70 F2.8


Any help or direction to a valid and new explanation of my question will be appreciated.

 

[vimwiz]

If your not shooting video, or bursts (Which you may be unlikely to if you were a film guy) the speed really doesnt matter.

I can believe that using both would be slower. Frankly, you would be better off with one faster one than two smaller, unless you like it as a backup.

See, the main problem on bodies isnt the cards themselve, but the buffer size. Youll probably fill it up just as fast writing to two than one.

 

[runnah]

Well you can either record to both cards, one at a time or sequentially. Some people shoot raw to one card and JPEG to another.

Video you can only record to one card at a time.

 

[RedStateRon]

Thanks to both of you, since it do shoot bursts now (to get hopefully one good pic of a grandchild) and will use as video , all answers have helped in my decision making.